1. Field of the Invention
The present invention relates to a numerical controller, and more particularly, to a numerical controller that performs automatic feed control based on a handle operation in a machine tool that includes a mechanical feed handle or a manual pulse generator-type handle.
2. Description of the Related Art
A machine tool with a numerical controller including a feed handle for operating a slide that moves a tool or a workpiece is known. FIG. 1 illustrates an example of such a system.
This machine tool 1 includes a mechanical handle or a manual pulse generator-type handle as a feed handle 3. The mechanical handle is configured such that the feed handle 3 is connected to a feed mechanism (not illustrated) of the machine tool 1 with a gear interposed therebetween. That is, the mechanical handle can be said to be a mechanism similar to an engine lathe or a milling machine used when an operator machines a workpiece manually. On the other hand, the manual pulse generator-type handle outputs pulse information corresponding to a rotation angle. The manual pulse generator-type handle is used in a state of being connected to a numerical controller 10, and the numerical controller 10 performs control of moving a slide 4 according to a handle operation.
In such a system, it is generally possible to execute both manual machining (a handle mode) which uses the feed handle 3 and automatic machining which uses a machining program by switching the mode of the numerical controller 10. In FIG. 1, reference numeral 20 denotes a motor, reference numeral 7 denotes a tool, and reference numeral 5 denotes a workpiece.
In general, when a plurality of same workpieces is machined, it may be efficient to create a machining program for a numerical controller to perform machining automatically. On the other hand, when a single workpiece is machined, it may be faster for an experienced operator to machine the workpiece (that is, to machine the workpiece manually using a feed handle) than automatic machining. Due to this, a machine tool with a numerical controller including the mechanical handle or the manual pulse generator-type handle is often provided.
The feed handle generally has a large reduction ratio in relation to a feed axis and has a small mount of feed per rotation angle of a handle in order to realize minute feed and positioning during manual machining. Due to this, in order to feed long stroke, for example, when a tool is released from the workpiece, it is necessary to continuously rotate the handle several times.
In order to obviate this, conventionally, when it is necessary to feed long stroke, an operator switches the mode of a numerical controller to a jog feed mode or a MDI program mode to release a slide using a jog feed button or a program command.
Japanese Patent Application Laid-Open No. 4-348843 discloses a technique in which a dedicated handle (lever) is provided in a machine tool so that long stroke can be fed continuously by an operator operating this lever.
However, in a method of switching the mode of the numerical controller, since the operator needs to operate the numerical controller, there is a problem that the operation efficiency deteriorates for an inexperienced operator. In this respect, although the configuration disclosed in Japanese Patent Application Laid-Open No. 4-348843 has an advantage that the operator is not aware of the mode switching of the numerical controller, there is another problem that the cost for providing the dedicated lever in the machine tool is necessary.